Recently, tunnel construction for forming tunnels by mechanically digging up and/or boring a base rock or the soil has been carried out at several places in order to use the tunnels for transportation for roads, railways, subways, and underground passages, watercourses for water supply and water use (irrigation, power generation, and water supply and sewage), transportation and underground storage of oil, underground pipe utility conduits for communication and electricity, underground storage of nuclear waste, mines, and military facilities.
Since such tunnel construction is very dangerous work, large and small accidents occur due to the blasting of explosives, occurrence of fire, or the movement of heavy equipment or the like when tunnel construction is carried out, and in particular, accidents affecting unauthorized laborers or foreign workers frequently occur in tunnels. To date, those in charge of safety in tunnel construction have made efforts to prevent accidents from occurring by detecting the locations of workers in a tunnel, the presence or absence of workers in a danger zone in blasting, and the entry and exit of an unauthorized worker. However, no suitable alternative plan, other than a method in which a person in charge of safety personally and visually checks such a situation, is present, because communication is not facilitated in the tunnel.
Therefore, there has emerged significant need for a system that is capable of detecting the locations of workers in a tunnel to prevent the occurrence of accidents in tunnel construction and a system that is capable of determining the last location of each worker to secure the golden time for rescue when an accident has occurred.